The present invention relates to a heat dissipation structure of an LED (light emitting diode) bulb and, more particularly, to a high-luminance SMD (surface-mount device) LED module featuring high heat dissipation.
For high-intensive illumination from an LED bulb, most LED manufacturers fabricate high-power LEDs (e.g., K2 LEDs manufactured by Lumileds) with high-lumen chips installed as light sources. FIG. 1 illustrates a conventional K2 LED 10 including a thermal conductive copper rod 14 on a base 12, which is used to support an LED chip 15 and which transfers heat generated by LED chip 15 through a large-sized thermal conductive bottom 16 of copper rod 14, and a plurality of solder terminals 18 for electric conduction, heat transfer and heat dissipation.
To share the market of high lumen LEDs, the SMD manufacturers are developing SMD LEDs with compact, high-current and high-lumen chips which have more advantages including manufacturing equipment, modules and manufacturing cost than K2 LEDs and are easily processed. FIGS. 2 and 3 illustrate a conventional LED 20 in which a thermal conductive fiber insulating layer 24 is deposited on an upper end face of a metal substrate 22 and covered by a plurality of separated conductive copper foils 25, 25-1. Two electric/thermal conductive electrodes 28, 28-1, an anode and a cathode, are provided on a lower end face of an encased LED 26 and are respectively fixed on two conductive copper foils 25, 25-1 for development of a conductive path. As one component for heat dissipation, fiber insulating layer 24, with much less thermal conductivity than that of metal material, weakens heat transfer from conductive copper foils 25, 25-1 to metal substrate 22. Furthermore, LED 26 fixed on metal substrate 22 conducts electricity and heat through electrodes 28, 28-1 restrictively and performs much worse thermal dissipation than K2 LED 10 in FIG. 1. Moreover, thermal dissipation through the copper foils with coatings (e.g., white paint as an antioxidant) spread on their upper end faces is attenuated.
The first priority to promote SMD LEDs in end use is the properties such as lumen and illumination comparable to those of conventional bulbs. Furthermore, the SMD LED bulbs as alternatives of conventional bulbs should be shrunk compared with other conventional bulbs. Therefore, the SMD LED bulbs with their sizes competing with those of conventional bulbs must upgrade the properties such as lumen, illumination and structure, all of which are taken as pivotal roles in the prospect of SMD LEDs in end use, for effective heat dissipation conforming to the standard of luminance decrease of an LED.
It can be seen from above descriptions that an effective heat dissipation structure developed for SMD LEDs is the target of all LED manufacturers.